use anyhow::Result;
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use tokio::sync::RwLock;
use tracing::info;

/// MCP server implementation
#[derive(Debug)]
pub struct McpServer {
    port: u16,
    is_running: bool,
    tools: RwLock<HashMap<String, Tool>>,
    clients: RwLock<Vec<ClientConnection>>,
}

/// Tool definition for MCP
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Tool {
    pub name: String,
    pub description: String,
    pub parameters: serde_json::Value,
    pub handler: String, // Function name to call
}

/// Client connection information
#[derive(Debug, Clone)]
pub struct ClientConnection {
    pub id: String,
    pub address: String,
    pub connected_at: chrono::DateTime<chrono::Utc>,
}

/// MCP request structure
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct McpRequest {
    pub id: String,
    pub method: String,
    pub params: serde_json::Value,
}

/// MCP response structure
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct McpResponse {
    pub id: String,
    pub result: Option<serde_json::Value>,
    pub error: Option<McpError>,
}

/// MCP error structure
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct McpError {
    pub code: i32,
    pub message: String,
    pub data: Option<serde_json::Value>,
}

impl McpServer {
    /// Create a new MCP server
    pub async fn new() -> Result<Self> {
        info!("Initializing MCP server");

        Ok(Self {
            port: 8080,
            is_running: false,
            tools: RwLock::new(HashMap::new()),
            clients: RwLock::new(Vec::new()),
        })
    }

    /// Create a new MCP server synchronously
    pub fn new_sync() -> Self {
        info!("Initializing MCP server (sync)");

        Self {
            port: 8080,
            is_running: false,
            tools: RwLock::new(HashMap::new()),
            clients: RwLock::new(Vec::new()),
        }
    }
    
    /// Start the MCP server
    pub async fn start(&mut self, port: u16) -> Result<()> {
        info!("Starting MCP server on port {}", port);
        
        self.port = port;
        self.is_running = true;
        
        // Register default tools
        self.register_default_tools().await?;
        
        // TODO: Implement actual server startup
        // This would involve setting up HTTP/WebSocket server
        
        Ok(())
    }
    
    /// Stop the MCP server
    pub async fn stop(&mut self) -> Result<()> {
        info!("Stopping MCP server");
        
        self.is_running = false;
        
        // TODO: Implement actual server shutdown
        
        Ok(())
    }
    
    /// Check if server is running
    pub fn is_running(&self) -> bool {
        self.is_running
    }
    
    /// Register a new tool
    pub async fn register_tool(&self, tool: Tool) -> Result<()> {
        info!("Registering tool: {}", tool.name);
        
        let mut tools = self.tools.write().await;
        tools.insert(tool.name.clone(), tool);
        
        Ok(())
    }
    
    /// Unregister a tool
    pub async fn unregister_tool(&self, name: &str) -> Result<()> {
        info!("Unregistering tool: {}", name);
        
        let mut tools = self.tools.write().await;
        tools.remove(name);
        
        Ok(())
    }
    
    /// Get all registered tools
    pub async fn get_tools(&self) -> Vec<Tool> {
        let tools = self.tools.read().await;
        tools.values().cloned().collect()
    }
    
    /// Handle an MCP request
    pub async fn handle_request(&self, request: McpRequest) -> McpResponse {
        info!("Handling MCP request: {}", request.method);
        
        match request.method.as_str() {
            "tools/list" => self.handle_tools_list(request).await,
            "tools/call" => self.handle_tool_call(request).await,
            "ping" => self.handle_ping(request).await,
            _ => McpResponse {
                id: request.id,
                result: None,
                error: Some(McpError {
                    code: -32601,
                    message: "Method not found".to_string(),
                    data: None,
                }),
            },
        }
    }
    
    /// Handle tools list request
    async fn handle_tools_list(&self, request: McpRequest) -> McpResponse {
        let tools = self.get_tools().await;
        
        McpResponse {
            id: request.id,
            result: Some(serde_json::to_value(tools).unwrap_or_default()),
            error: None,
        }
    }
    
    /// Handle tool call request
    async fn handle_tool_call(&self, request: McpRequest) -> McpResponse {
        // TODO: Implement actual tool execution
        // This would involve calling the appropriate handler function
        
        McpResponse {
            id: request.id,
            result: Some(serde_json::json!({
                "content": "Tool executed successfully",
                "isError": false
            })),
            error: None,
        }
    }
    
    /// Handle ping request
    async fn handle_ping(&self, request: McpRequest) -> McpResponse {
        McpResponse {
            id: request.id,
            result: Some(serde_json::json!("pong")),
            error: None,
        }
    }
    
    /// Register default database tools
    async fn register_default_tools(&self) -> Result<()> {
        // Query execution tool
        let query_tool = Tool {
            name: "execute_query".to_string(),
            description: "Execute a SQL query against the database".to_string(),
            parameters: serde_json::json!({
                "type": "object",
                "properties": {
                    "sql": {
                        "type": "string",
                        "description": "The SQL query to execute"
                    },
                    "database": {
                        "type": "string",
                        "description": "The database connection name"
                    }
                },
                "required": ["sql"]
            }),
            handler: "execute_query".to_string(),
        };
        
        // Schema inspection tool
        let schema_tool = Tool {
            name: "get_schema".to_string(),
            description: "Get database schema information".to_string(),
            parameters: serde_json::json!({
                "type": "object",
                "properties": {
                    "database": {
                        "type": "string",
                        "description": "The database connection name"
                    },
                    "table": {
                        "type": "string",
                        "description": "Specific table name (optional)"
                    }
                }
            }),
            handler: "get_schema".to_string(),
        };
        
        // AI SQL generation tool
        let ai_tool = Tool {
            name: "generate_sql".to_string(),
            description: "Generate SQL from natural language".to_string(),
            parameters: serde_json::json!({
                "type": "object",
                "properties": {
                    "prompt": {
                        "type": "string",
                        "description": "Natural language description of the query"
                    },
                    "schema_context": {
                        "type": "string",
                        "description": "Database schema context (optional)"
                    }
                },
                "required": ["prompt"]
            }),
            handler: "generate_sql".to_string(),
        };
        
        self.register_tool(query_tool).await?;
        self.register_tool(schema_tool).await?;
        self.register_tool(ai_tool).await?;
        
        Ok(())
    }
    
    /// Add a client connection
    pub async fn add_client(&self, client: ClientConnection) {
        let mut clients = self.clients.write().await;
        clients.push(client);
    }
    
    /// Remove a client connection
    pub async fn remove_client(&self, client_id: &str) {
        let mut clients = self.clients.write().await;
        clients.retain(|c| c.id != client_id);
    }
    
    /// Get connected clients count
    pub async fn client_count(&self) -> usize {
        let clients = self.clients.read().await;
        clients.len()
    }
}
